This invention relates in general to the handling of optical signals and, more particularly, to configurations in which several optical fibers are associated with respective collimating lenses.
Telecommunications is a field which has been rapidly evolving over the past twenty years, fueled in part by the progressively increasing popularity of technologies such as cellular telephones, facsimile machines, and computer communications that use the Internet. Due to these growing new technologies, there has been a progressively increasing demand for telecommunications equipment with greater information-carrying capacity, which in turn has created a progressively increasing focus on effecting communications through the use of optical signals.
High bandwidth fiber optic telecommunication systems are being deployed around the world. This is creating a backbone system which couples major metropolitan areas. Currently, when these existing systems need to effect switching of an optical signal, they typically convert the optical signal into an electrical signal, effect electrical switching of the electrical signal, and then convert the resulting electrical signal back into an optical signal. This greatly delays the propagation of information through the system, and is expensive because it increases the complexity of the system.
In order to avoid this problem, attempts are being made to develop optical switches which would directly switch optical signals, without temporarily converting them into electrical signals. While existing approaches to optical switching have been generally satisfactory for their intended purposes, they have not been satisfactory in all respects.
For one example, one existing type of optical switch is known as a two-dimensional optical cross connect (OXC) switch. It has a hermetically sealed housing that contains a digital micromirror device (DMD), which is also sometimes referred to as a micro-electro-mechanical system (MEMS) device. The DMD has a plurality of movable mirror parts arranged in a two-dimensional array. The hermetically sealed housing includes two transmissive windows arranged at an angle to each other. Externally of the housing, two plates each have several V-shaped grooves that are formed by diamond point turning and that extend perpendicular to a respective one of the windows. Each groove has a collimating lens mounted therein at a location spaced from the associated window, and has an optical fiber end mounted therein, often at a location spaced from the collimating lens. Radiation traveling through one of the optical fibers can exit the end of that fiber, pass through the associated collimating lens, pass through the associated window, undergo reflection by a respective mirror part of the DMD, pass through the other window, pass through another collimating lens, and then enter another optical fiber.
In this type of device, insertion losses from an input fiber to an output fiber are relatively high, and are typically on the order of 3 dB to 4 dB. This is due in part to the fact that various individual components have sufficient differences in their coefficients of thermal expansion so as to generate significant alignment errors across the operational temperature range of the switch. Further, even for a given temperature, it is complex and time-consuming to attempt to achieve suitable alignment of the multiple independent components during assembly of the switch, as a result of which these existing switches are relatively expensive to make, and the production yields are relatively low. Also, even though the windows theoretically have no optical power, in practice they are non-ideal and may each have a slight wedge shape that introduces a small optical power.
A further consideration is that environmental conditions such as vibration and shock can produce dynamic alignment problems between the multiple components. Still another consideration is that there are a number of optical surfaces that are susceptible to environment factors such as dust, moisture and outgassing of plastic or adhesive materials used to couple the various components together. These optical surfaces typically include the end surface of each fiber, two end surfaces of each collimating lens, and the outer surface of each transmissive window.
From the foregoing, it may be appreciated that a need has arisen for a method and an apparatus that reduce susceptibility to insertion loss and/or environmental factors in a context wherein optical fibers are associated with respective lens structures. According to one form of the present invention, a method and apparatus are provided to address this need, and involve: supporting a plurality of optical parts on a base; adjusting a lens section to a selected position with respect to the base, the lens section including a support portion made of an optically transmissive material, and including a plurality of lens portions made of an optically transmissive material and provided at spaced locations on a first side of the support portion, the lens portions each being aligned with a respective optical part in the selected position of the lens section; fixedly securing the lens section in the selected position with respect to the base; positioning an end of each of a plurality of optical fibers to be adjacent the support portion on a second side thereof opposite from the first side, and to be in an alignment position with respect to a respective lens portion; and fixedly attaching the end of each fiber to the second side of the support portion.